A “time-of-flight” camera is a depth-sensing or range-sensing system that operates by illuminating a scene using a light source (e.g., a modulated source of light at any wavelength or frequency, such as infrared) and capturing light that is reflected from various points of the scene following the illumination. Time-of-flight cameras are typically equipped with an illuminator for illuminating a scene, and a sensor for capturing reflected light from the scene. The reflected light that is captured by a time-of-flight camera sensor may be interpreted to generate a depth profile of portions of the scene within a field of view of the time-of-flight camera. Some time-of-flight cameras may capture and interpret reflected light, and generate depth images or profiles of portions of scenes from such reflected light, several dozen times per second. Depth images or profiles generated by time-of-flight cameras can be very accurate.
Occasionally, where two or more time-of-flight cameras are mounted at scenes with overlapping fields of view, care must be taken when operating the time-of-flight cameras. Where an illuminator of a first time-of-flight camera illuminates a scene, and a sensor of a second time-of-flight camera having an overlapping field of view is exposed, reflections of the light projected onto the scene from the illuminator of the first time-of-flight camera may be detected by the sensor of the second time-of-flight camera, thereby resulting in a false construction of a depth profile by the second time-of-flight camera. To alleviate this effect, the operation of multiple time-of-flight cameras may be synchronized. Where two or more time-of-flight cameras are mounted with overlapping fields of view, the times at which such cameras operate illuminators to illuminate scenes and expose sensors to capture reflected light from such scenes may be sequenced (or staggered) to ensure that a sensor of a time-of-flight camera is exposed only at times when an illuminator of that time-of-flight camera has illuminated a scene, and not at other times, e.g., when an illuminator of another time-of-flight camera has illuminated the scene.
Synchronizing the operation of multiple time-of-flight cameras having overlapping fields of view may be performed where the time-of-flight cameras operate under the control of, and are in communication with, a common computer device. In such environments, the time-of-flight cameras may be operated according to a network timing protocol that controls the illumination of a scene by an illuminator and the capture of reflected light by the exposure of a sensor for each of the time-of-flight cameras. Synchronizing the operation of multiple time-of-flight cameras is not presently feasible, however, where the time-of-flight cameras are not connected to a common computer device, or otherwise may not be operated according to a network timing protocol. Such environments may include, for example, scenes having a large number of time-of-flight cameras mounted with overlapping fields of view, or where time-of-flight cameras are mounted aboard independently operated machines such as autonomous mobile robots or unmanned aerial vehicles, such that fields of view of such cameras overlap for brief or unpredictable periods of time.